Revenues should finish at $4.27 billion from the first weekend in May through Labor Day, down 3 percent from the record of $4.4 billion set last summer

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"The Avengers" took in $618 million domestically and the Batman finale "The Dark Knight Rises" so far has added about $430 million, their $1.05 billion total amounting to nearly one-fourth of Hollywood's overall summer haul.

Studio executives expected their biggest summer ever this year as they loaded their lineup with huge action movies and superhero franchises.

What they got were two colossal blockbusters, a handful of backup hits and plenty of duds that just didn't deliver, resulting in what may prove the lowest summer movie attendance in 20 years.

While domestic revenues are projected to come in as the second-best ever, the number of tickets sold shrank to about 532 million from the first weekend in May through Labor Day, down 4 percent from summer 2011, according to box-office tracker Hollywood.com. If that holds by the time final ticket sales are counted through Monday, that would be the smallest audiences Hollywood has packed in for its busiest season dating back to 1993, the earliest summer revenue data maintained by Hollywood.com.

Revenues should finish at $4.27 billion from the first weekend in May through Labor Day, down 3 percent from the record of $4.4 billion set last summer, said Hollywood.com analyst Paul Dergarabedian.

"On paper, the summer of 2012 looked like a clear record-breaker. I think a lot of us were expecting we could beat last summer just based on the titles, the sheer number of blockbuster titles that were in the mix," Dergarabedian said. "But the audience is what makes and breaks the summer, and they didn't come out in the numbers we expected for a lot of these films."

Summer was ending quietly over Labor Day weekend, with overall revenues through Sunday down slightly compared to the same period a year ago. Domestic sales totaled $102 million, off 4.6 percent from last year's Labor Day weekend, according to Hollywood.com.

The horror tale "The Possession" debuted as the No. 1 movie with $17.7 million from Friday to Sunday, compared to $14.6 million for the top draw a year ago, "The Help," which joined "Rise of the Planet of the Apes" to give Hollywood a strong seasonal finish that made summer 2011 a record-breaker.

Before this summer arrived, Hollywood was on a box-office tear, with revenues up as much as 20 percent over 2011's. Studio executives hoped that would continue into summer, when they had what looked like the best lineup they've ever offered.

Instead of beating last summer's record, though, revenues for the season fell for the first time in seven years.

The picture gets worse factoring in higher admission prices. While revenues this time were well above the $3.6 billion haul in 2005, the last time summer dollars dipped, this season's estimated 532 million admissions is well below the 563 million tickets sold in summer 2005.

In the 20-year span since 1993, Dergarabedian said the only year that comes close to this season's attendance was summer 2010, when 534 million tickets were sold. A strong Labor Day weekend could put this summer on par with 2010 attendance, but it's still a soft season considering expectations at the start, when the superhero sensation "The Avengers" launched with a record $207.4 million debut over the first weekend in May.

"The beginning of summer is like the first day of spring training or the opening of football camp. You have to hope your summer's going to be great," said Dave Hollis, head of distribution at Disney, which released "The Avengers." ''But it's hard to say what's going to connect or click."

"The Avengers" took in $618 million domestically and the Batman finale "The Dark Knight Rises" so far has added about $430 million, their $1.05 billion total amounting to nearly one-fourth of Hollywood's overall summer haul. Worldwide, "The Avengers" has pulled in $1.5 billion, while "The Dark Knight Rises" soon will cross the $1 billion mark.

Summer's third superhero saga, "The Amazing Spider-Man," climbed to $258 million domestically, while the animated adventures "Brave" and "Madagascar 3: Europe's Most Wanted" both were $200 million hits. The raunchy talking teddy bear comedy "Ted" also topped $200 million, and summer produced solid successes with "Men in Black 3," ''Snow White and the Huntsman" and a few other $100 million movies.

Yet a lot of duds accompanied the hits, with flops such as "Battleship" and "Total Recall" leaving audiences cold. Star power could not pack theaters, either, as fans generally ignored movies featuring A-listers ("That's My Boy" with Adam Sandler, "Rock of Ages" with Tom Cruise, "Dark Shadows" with Johnny Depp, "The Watch" with Ben Stiller and Vince Vaughn).

The international box office has been Hollywood's growth area as overseas audiences become more eager for big studio flicks. "The Avengers" did nearly 60 percent of its business overseas. "The Dark Knight Rises" has taken in well over half of its revenues internationally, the reverse of 2008's "The Dark Knight," which pulled in most of its cash from domestic crowds.

Domestic summer movie attendance hit a modern high of 653 million in 2002, when "Spider-Man" opened with a then-record $114.8 million. Hollywood has continually climbed to new dollar highs since, but actual attendance has steadily declined as entertainment options expanded with home theater systems, streaming video and endless portable gadgets.

This season, the Summer Olympics siphoned off movie audiences a bit, and the shootings that killed 12 people at a midnight debut screening of "The Dark Knight Rises" in Colorado jolted the industry.

Studio executives say the shootings probably cut into business by no more than a fraction. The tragedy did prompt some moviegoers to think twice about heading to theaters when they have so many entertainment options right at home, though.

The upside for Hollywood is that revenue and attendance for the year is 4 percent ahead of 2011's, while attendance is up 3 percent. Hollywood hopes to build on that with a strong fall and holiday lineup that includes the James Bond thriller "Skyfall," the "Twilight" finale and part one of "The Lord of the Rings" prelude, "The Hobbit: An Unexpected Journey."

Of course, studio bosses had the same hopes for summer before business took a downturn.

"We had a couple of movies ourselves that didn't meet expectations," said Dan Fellman, head of distribution at Warner Bros., which released "The Dark Knight Rises" and the surprise hit "Magic Mike" but also stumbled with "Rock of Ages" and "Dark Shadows." ''There's the old cliche, nobody starts out to make bad movies. But we are looking at a very strong fall and Christmas ahead."